Characteristics and Influencing Factors of Soil Carbon Flux in Suburban Forest and Grassland in Lanzhou

  Objective  The paper aimed to explore the variation of soil carbon (C) flux in suburban forest and grassland in Lanzhou, and quantitatively estimate soil C emission, so as to provide reference for the study of C emission and C cycle in urban and suburban areas.

  Method  In this study, locust, alfalfa and Sandgrass were used as experimental plots in "Xiaoqingshan Soil and Water Conservation Science and Technology Demonstration Park" in the suburbs of Lanzhou. LI-8150 "Soil carbon flux measurement system" was used to continuously monitor the soil C flux of three kinds of forests and grasslands, analyze the characteristics of soil C release, and clarify the correlation between soil C flux and influencing factors.

  Result  ①The highest value of soil C flux occurred at about 14:00 in the afternoon, and the lowest value occurred at about 6:00 in the morning. The soil C flux values at 10:00 AM and 20:00 PM were basically consistent with the daily average. The annual total soil C emission of alfalfa was 2321.30 g m^-2, which was 1.24 times higher than that of robinia pseudoacacia forest and 1.48 times higher than that of astragalus pastures. ②The changes of land surface temperature and 5 cm soil temperature were consistent among the three kinds of forest and grassland, and there was no significant difference (P > 0.05). The soil C flux had a significant positive exponential relationship with surface temperature and 5 cm soil temperature (P < 0.05), and the soil C flux in robinia pseudoacacia forest had the highest sensitivity to temperature. ②Soil C flux of forests and grasslands was significantly correlated with solar radiation (P < 0.05), soil C flux of artificial Robinia perseudoscacia was significantly correlated with rainfall (P<0.05).

  Conclusion  The highest soil C flux is found in the forest and grass fields in the suburb at around 14:00 in the afternoon, and the highest soil C emission is found in the alfalfa grass fields. Temperature and solar radiation intensity are significantly correlated with soil C flux（P < 0.05）.